Commutating reactor



Jan. 19, 1960 P. scHNEcKE COMMUTATING REAcToR Filed Jan. 9, 1956 3Sheets-Sheet 1 abc sa. w W

Jan; 19, 1960 P. scHNEcKE 2,922,133

COMMUTATING REACTOR Filed Jan. 9, 1956 3 Sheets- Sheet 2 WMM, M

Jin. 19, 1960 P. scHNEcKE 2,922,133

coMMuTATmG REAcToR Filled Jan. 9, 195e s sheets-sheet :s

PAI/1 sc//NCKE BY Qa-M MQ, M @1252 lactors are inserted in series withthe contacts. Aactors have a substantially square shaped, so-called hys-United States Patent O COMMUTATING REACTOR Paul Schnecke,Berlin-Siemensstadt, Germany, assignor to Siemens-Schuckertwerke A.G.,Berlin and Erlangen, Germany, a corporation of Germany ApplicationJanuary 9, 1956, Serial No. 558,112

Claims priority, application Germany January 10, 1955 Claims. (Cl.336-180) My invention relates to a toroidal winding for reactors havingan enclosed core and more specifically to a cornmutating reactor forapplication with mechanical and electromagnetic rectifiers of the typeshown in copending applications Serial No. 257,398, i-led November 20,1951, now Patent No. 2,756,380, and Serial No. 301,880, filed July 3l,1952, now Patent No. 2,759,128.

A mechanical rectifier produces direct Voltage by making metalliccontact betwe-ena proper phase of an A.C. system and the associated D.C.system during the time interval the particular phase of the A.C. systemis capable of delivering energy in the desired direction, and breakingthe metallic contact when the A.C. phase reverses its voltage inrelationship to the D.C. voltage. This operation is performedsequentially and repeatedly in synchronism with the A.C. frequency.

The metallic contacts which perform the switching are switches which areable to carry the full current which flows through the rectifier. Thesecontacts, when open, are able to withstand the full inverse voltage,when the alternate voltage is opposed to the direct voltage. But theycannot interrupt a current greater than a fraction of one ampere withoutsuffering 'a slight damage. Due to the periodical operation of theswitches (they must each operate 60 times per second in a 60 cyclesystem), the slight damage to the contact, if they are called upon tointerrupt any substantial current soon accumulates to a totaldestruction of the contact surface.

Another limitation is the inrush current after closing the contact. Acontact does not close instantly. During closing the contacts touch verylightly over a small area thus providing a high resistance. As thecontacting area and pressure increases, the contact resistance iscorrespondingly reduced. The time required for this phenomenon is twentyto thirty microseconds. If a high current is permitted during thisinterval, the narrow contact area will melt and thus be the cause oftransfer of metal. Furthermore, the contact might rebound partially ortotally after approximately one hundred microseconds. If the reversemotion is strong enough to reduce the contact pressure appreciably, somemore transfer of metal will ensue. The transfer. of metal will again bethe cause of destruction because it is cumulative. To use such a switchas a mechanical rectifier, without any additional protective equipmentwill immediately result in its destruction.

To prevent such damage, saturable commutating re- These reteresis loopwhich present high resistance at low current and thus limit the inrushcurrent after closing, and the residual current before opening, to asufficiently low value change. of ux very large and accordingly thereactance of the saturable reactor very large compared to a normal load.The amplitude of the current flowing in the system instead of changingin accordance with the normal sinewave is, therefore, held at acomparatively low value during the switching interval.

The main winding of the commutating reactor must be designed to carrythe full load current of the mechanical rectifier. rIhus in commercialapplications these windings must have sufficient cross-sectional area tocarry rectified load currents of the magnitude of 5,000 and 10,000amperes. These windings are Wrapped around a cylindrical core ofPermeron. The Permeron core material, having a composition of 40 to 50%Ni, has a flux-charge characteristic which closely approaches those ofan ideal magnetic material and thus has a high impedance whichfluxcharge is taking place and negligible impedance when the core issaturated. The effect is to restrain current (step length) flow whilethe magnetization is making a complete reversal in either direction andto permit full current flow the instant the core is saturated. The mainwinding is wound on this hollow cylindrical core parallel to the axisthereof with each completed turn of the conductor on the outside andinside surface of the hollow cylinder.

However, if a uniform gage conductor is used for the windings the insidesmaller circumference of the hollow cylindrical core would have toaccommodate the same quantity of large cross-sectional conductors as thelarger outside circumference and would therefore necessitate a largecumbersome cylindrical core. In practice it has been found that thelarge core which would thus be required would be uneconomical, a wasteof space, impractical from the point of view of manufacture andinstallation; and furthermore could not be practically assembled in acommon casing with the transformer as will hereinafter be more fullyexplained.

Furthermore, the large core required by conductors of uniformcross-section has one basic magnetic disadvantage. Namely, the meanlength of the magnetic path in the Permeron core material would be toohigh resulting in an excessive magnetizing current which in turnwouldresult in an excessive contact current. However, with my presentinvention reduction of mean length of magnetic path is of the order of50%.

My invention relates to a novel and inventive structural arrangement toovercome the above enumerated disadvantages which result from thenecessity of using a large cylindrical core in order to providesufficient space requirements on the inside circumference for conductorsof uniform cross-sectional area.

More specifically, my invention utilizes an inner conductor as a part ofthe continuous toroidal winding, wherein the peripheral length of theinner conductor is relatively large and the radial dimension of theinner conductor is relatively small. In view of the relatively smallradial dimension, it is now possible to maintain eddy current effects toa minimum and the presence of the relatively large peripheral dimensionassures the appropriate cross-sectional area required for currentconduction. In view of the increased peripheral dimension, however, Ifind that at least one of the inner conductors must be radiallydisplaced from the other conductors, since if this were not the case,the total circumferential dimension of the inner conductors would exceedthe available circumferential dimension of the inner diameter of themagnetic core.

In a more specific case, I have found it desirable to radially displacethe inner conductors of adjacent turns from one another, wherein a firstand second layer of inner conductors is provided, with the opening ofthe magnetic core, and the inner conductors of adjacent turns overlapone another.

This novel principle may be further extended to the secarse 3 case,where the inner conductors of the toroidal windings on the magnetic coreare shaped in the form of a hollow cylinder. Hence, in the 1'case of -aplurality of inner conductors',

there will be a plurality of concentric hollow conductors',V

which are cyclically connected to the outer conductors by means ofconnecting members. Here again, the radial dimension of each of thehollow cylinders is relatively small to maintain low eddy current eiectwhile the circumferential d-imension of the turn is relatively largecompared to the radial dimension, so as to maintain a sutncientcross-sectional area for current conduction.

Accordingly, the primary object of my invention is to provide a toroidalwinding for an enclosed magnetic core.

Another object of my invention, is to provide a reactor having anenclosed magnetic core and a toroidal winding, wherein at least one ofthe inner conductors of the winding is radially displaced from the otherinner conductors.

Another object of my invention, is to provide a toroidal winding whereinat least one of the inner conductors is radially displaced from thevother inner conductors, and is in overlapping relationship with one ormore of the other inner conductors. v

Another object of my invention is to provide a'toroidal winding forcommutating reactors, wherein eddy current eects in the inner conductorsis substantially decreased by constructing the inner conductors to bepositioned in an overlapping relationship, and to maintain a relativelysmall radial dimension for the inner conductors. K

A still `further o bject of my invention is to provide a reactor khavingan enclosed core and a toroid'al winding wound thereon, wherein theinner conductors of the tridal iri'ndrg 'are kconcentric hollowcylinders, having a relatively small 4radial dimension. Y v

These and `other objects vof my invention v'will befa'p- ,parent fromthefollowing description when vtaken in connection with the drawings inwhich:

Figure f1 4is a schematic electrical diagram of a me chanical rectifier,which could utilize commutating refactors constructed in accordance withmy novel invention.

Figure l2` is a perspective view o'f the push-rod assembly and contactassembly of lthe contact converter for the mechanical rectifier.

Figure 3 shows a top view of a reactor havinga toroidal windinglconstructed in accordance vv'ith my novel invention. v

Figure 4 shows :the view 'of Figure 3, with the upper conducting membersbroken away to afford observation of the inner and outer conductors. Y l

Figure 5 is a further view similar to Figure 3, wherein `the connectingVconductors at the bottom of the core are shown as dotted lines, and allof the upper conductors have been broken away. p n yFigure 6 is a viewin perspective of the vhollow cylindrical core utilized inthe reactor ofmy invention.

Figure 7 a yhysteresis loop for the reactor utilizing the core Yof'Figure "6.

Figure 8 is a top view'of a second embodiment of my novel toroidalwinding, wherein the inner conductors vare hollow concentric cylinders.

Figure 9 is a sectional view of Figure 8, taken 'acc'ss the 'lines 9--9.

The source `ofalternating current .is taken .from .the `alternatingcurrent lines -10 through the circuit breaker 11 to step downtransformer 12. The source current -is then passed vthrough rthevcommutating reactors 13 to step `the 'current 'for switching purposesas ksetforthzin 'application Serial No. 212,017 tiled February 21,195:1.

The 'current passes through disconnect switches :1:4 to the 'contactconverter 15. The Ycontact converter "I5 sequentially and repeatedly insynchronis'mwith the'fAiC.

frequency Y'connects Ithe alternating current source buses vannealingtemperatures.

4 10a, b, c, to the D.C. load buses 20-21 and load 5 through the D.C.protective equipment 132.

The bridge connected contact converter 15 may contain two sets ofcontacts, (not shown) a negative set and a positive set. The two setsofcontacts are oiset 180 electrical degrees from each other and thecontacts in either positive or negative set for all the phases a, b andc are vset apart. three phase voltage a, b, c and at one period of timethe load current will flow from phase a, through a positive contact,through the load and back over a negative contact. During positivecommutation between phases a and b, the load current divides betweenthesetwo phases by simultaneously closed positive cont-acts.

For the purpose of simplification, I have shown in Figure 2 theswitching structure which is used at phase a, it being understood Ythatthe switch apparatus for phases b and c are identical in construction. nThe details of the contact assembly units 71, 72 are described in mycopending application Serial No. 307,067, filed August 29, 1952, and thedetails of the push rod assembly 62 and 63 are described in copendingapplication Serial No. 307,024, filed August 29, 1952.

In operation, energy from the generator 1 -is fed through the powertransformers 11 to the main winding itV o'f the commuta'ting reactor 13and to the load 5 b'y means of closed contacts 4in the contact'converter 15. The 'commuta'ting reactor 13 consists of ialcoil 3 ofconducting material and a core -33 which is saturable at relatively lowcur-rent values. Thecore is made of wound tape, as seen Yin Figure 6,and therefore has no air gap. `By reason of the use of a tape, themagnetic flux ows in the circumferential'direction of the wound tape.Accordingly, the Aflux does not ycross any air gaps. ln order to lreduceeddy currents, the tape is fmade extre'melythin, being usually of the:order of from 0.001 te 0;002 inch thick. n

The coil around A'the core should be Wound as "tightly 'as possible.This permits the use'o'f a small `-'core A.for a predetermined amount ofwire that Vmust be used; it also reduces `the reactance ofthe core whenthe core is saturated and the coil assumes the properties of an -airreactor of the same dimensions.

The bestcore material for commutating reactors -known up to now isvacuum fused 50% iron, 50% nickel alloy, and must not contain anyimpurities such a's oxygen, carb'on, other metals, etc. In order tomaintain its crystallini'c structure, it should not be deformed afterannealing. Insulation such as magnesium oxide is provided betweenthelayers of the tape of the property to withstand the The tape is coldrolled down to -the 'final thickness and annealed 'at 1950 F. -inelectrolytic hydrogen with no water vapors present. Y

The outstanding property of a -commutatin'g Preactor' is 'the greatA'variation in physical behavior it affords at different currents.Whenever Vthe total ampere-turns around vthe VVreactor core are higherthan Ia predetermined minimum, the reactorr behaves exactly as if itwere a copper coil wound around va non-magnetic core; It

has y-a predetermined vresistance and reactance offre'la'tively lowvalue.

As soon asthe total ampere-'turns are Vreduced E'toriear zero andchanged into the opposite direction, the-'reactor "snddenlyassumesareactance which is"50,0'00'-or1100,000 higher than at thelargercurrents. "I'his'tran'sition happens always atthe same currentvalue and -is 'instantaneous.

A high voltage must nnow be applied to 'fthe Winding of the coil whichcarries only 'a VK'very 'fsmall `"current,

i.e.,*the -so-called magnetiz'ing current. This ycurrent is almostconstant and is almost independent df thef'v'ciltnage' applied. Thisperiod Aof high reactance lasts `for a relatively "short vtime'interval' in each cycle 'with vthe feitactly *defined condition`'-th'atithe vonage applied to fthe ccnl, tintes tti-is'rltiime`iritervatintalways-fccmstarrt. *'Arter The circuit may be supplied withthe end of lthe time interval, the coil has again the properties of anair core reactor, the core reactance becomes negligibly small and thecurrent suddenly rises again to a value which is limited only byexternal means, such as a load.

The proportion of the abnormal behavior of the commutating reactor isusually described by its fluxcurrent curve shown in Figure 7,inappropriately called hysteresis loop. This curve (Figure '7) resemblesa rectangle with the horizontal parts (extending to the infinite)indicating the normal low reactance behavior and the -almost Verticalparts indicating the high reactance part.

This latter portion is characterized by the low current which cannot beallowed to increase during the above mentioned time interval. Thiscurrent is called magnetizing current, or step current, and the timeinterval the step length, i.e., the time during which the current isactually frozen, to the small value of the step current. The stepcurrent of practically used commutating reactors is less than onethousandth -of the peak current, lthe step length approximately oneone-thousandth second and the rise of the` uX after the end of the stepis less than 4% of the step length.

From the above, it will now Vbe clear that during most of the currentcycle, as for example, current values from 25 (Figure 7) and higher, thereactor is saturated. Accordingly, as shown, there is no flux change andthe reactor presents substantially no impedance to the circuit.Accordingly, during this portion of the cycle, all or almost all of thevoltage of the generator 1 appears across the load 5.

However, during a relative small part of the cycle when the current hasjust passed through zero value reversing its polarity from positive tonegative as at 2l (Figure 7) and is increasing to 22, commutatingreactor 13 is saturated. At this low current value, due to rapid changein flux from 21 to 22 (Figure 7) the reactor 13 presents a very muchhigher reactance than the load. Due to this high impedance, the currentis held low and all or substantially all the voltage of the generatorappears across. the reactor.

The iirst embodiment of my novel winding may be seen in conjunction withFigures 3, 4 and 5, in which Figure 3 shows a top view of a toroidalwinding encircling an enclosed magnetic core, which could be of the typeshown in Figure 6. Figure 4 is a view of Figure 3 with the uppermostconductors which connect the inner and outer conductors removed toalford observation of the manner in which the under layer of upperconductors connect their respective inner and outer conductors, andFigure 5 is another top view of Figure 3 wherein all yof the upperconductors are removed and connections at the bottom of the reactor areindicated in dotted lines.

In each of Figures 3, 4 and 5, it is seen that a tirs-t terminal 80 isconnected to the upper conductor member 81, and this upper conductormember 81 is then connected in turn to the inner conductor 82. Asspeciiically seen in Figure 5, the inner conductor 82 is connected atits bottom to a connecting member 83 which then goes to the bot-tomouter conducting member 84. The top of conductor 84 is then connected tothe connecting member 85 of Figure 3, which passes over the connectingmember 81 and is connected to the top of inner conductor 86. From thebottom of inner conductor 86, a connection is then made to the bottom ofthe outer conductor 87.

It is to be noted that the two inner conductors 82 and 86 are radiallydisplaced from one another and are in overlapping relationship with oneanother. By providing this type of construction, it is seen that theradial dimension of the inner conductors 82 and 86 may be small as theirperipheral dimension is large,

. and still maintain a predetermined cross-sectional area.

The toroidal winding is then completed in a manner as has beenpreviously described and the cyclic connection, which may be best seenin Figures 4 and 5 is made in the conductor sequence of outer conductor87, inner conductor 88, outer conductor 89, inner conductor 90, outerconductor 91, inner conductor 92, outer conductor 93, inner conductor94, outer conductor 95, inner conductor 96, outer conductor 97, innerconductor 98 and iinallyr the second terminal 99.

The conductors which interconnect the inner and outer conductors at thetop, may be specifically seen in Figure 3, where the top conductorconnects the inner and outer conductors 84 and 86, the top conductor 100connects the inner and outer conductors 88 and 87, conductor 101connects the inner and outer conductors and 89, top conductor 102connects inner and outer conductors 92 and 91, top conductor 103connects inner and outer conductors 94 and 93, top conductor 104connects inner and outer conductors 96 and 95 and finally, the topconductor connects the inner and outer conductors 98 and 97.

It is to be understood that the same type of connection between theinner and outer conductors would be alforded at the bottom of thereactor winding and will not be set forth here.

It is seen that in the winding shown in Figures 3 through 5, that theinner conductors are positioned along two radial diameters. In view ofthis novel positioning their peripheral lengths may be increased,whereby their radial dimension is decreased in order to minimize eddycurrent effects.

The second embodiment of my novel invention may be seen with referenceto Figures 8 and 9, wherein the inner conducting members of the toroidalwinding comprise a plurality of concentric hollow cylinders. Morespecifically, Figure 8 shows a winding having the terminals 110 and 111wherein the terminal 111 is connected to the tubular inner conductor 112at the protruding portion 112e of the conductor 112. This connection isfacilitated by projecting portion 112a of the conductor 112 to a greaterheight than the height of the adjacent tubular inner conductors in themanner shown in Figure 9. The bottom of the tubular conductor 112 isthen provided with a similar projection seen in Figure 9 as projection112b, which is electrically connected to the bottom of the outerconductor 113, to complete the iirst turn. The top of conductor 113 isthen connected to the tubular conductor 114 at the projection portion114:1 at thetop of the tubular conductor 114, and the bottom of theconductor 114 is then attached to the next outer conductor, seen inFigure 8 as the outer conductor 115. Outer conductor 115 is thenconnected to the top of the tubular conductor 116, which in turn isconnected to the bottom of the next outer conductor and this process iscontinued until the winding is completed, and the last inner conductor117 is connected at its bottom protrusion 117a to the second terminal110.

It is to be realized that each tubular inner conductor is, of necessityinsulated from the next conductor in order that the winding is not shortcircuited.

Furthermore, since the inner conductors having a larger diameter mayhave a smaller radial dimension for the cross-sectional area, the radialdimension of the inner conductors may be decreased as they arepositioned at further radial positions.

It is of interest to note that in the case of Figure 9, it isillustrated that the magnetic core may be comprised of four individuallywound cores 116a, 117b, 118 and 119. The cores 116 through 119, arefurther seen as being encased in an insulated housing 120, and thewindings are then placed around this insulated housing 120.

The portion of the winding which connects to the inner conductor, suchas conductor 113, is more specically shown in Figure 9, as comprising acontinuous U-shaped ends are then fashioned in such a form that theconnecting sectional area; said inner conductors being formed from!"ends are twistedb-y 9l)1 and oier a relatively' large surface forWelding or soldering operation.

I t is to be noted that this oiers a considerably simpli-V fiedmanufacturingprocedure in which the `upper and lower legs of theU-shaped winding lie inl intersecting planes. Y

1n the foregoing, I have describedmy invention only in connection withpreferred special embodiments thereof. Many variations and modificationsof the principles oi my invention within the scope of the descriptionherein are obvious. `Accordingly,1" prefer to be bound not by thespecific'disclosurev hereinrbut only by the appending claims Y Y Iclaim; f

1. A comnintatin'g'reactor comprising a ring shaped core Qfthighlysaturable type magnetic material and a torcidal vi/inding wound thereon;said toroidalvwinding comprising 'plurality 'of conductors of smallradial dimension positioned within the opening formed bysaid ring shapedcore, a plurality of outer conductors, and connectf ing conductors; saidconnecting conductors beingco'nstructed to interconnect said pluralityof inner and outer conductors cyclicaily to form a continuous'conductorof toroidal form; the inner conductors of adjacent turns beingrespectively formed from a rsrt and second hollow conductive cylinderheld in insulated relationship with respect to one another; the innerconductors of adjacent tur-ns of said continuous toroidal winding beingradially displaced from one another and overlapping one another in aperipheral direction; a substantially large cross-sectional area ofisaidinner conductors thereby being obtained by maintaining a relativelysmall radial dimension to decrease eddy current eiects and providing arelatively large peripheral dimension.

2. A commutating reactor comprising a ring shaped core of highlysaturable type magnetic material and a toroidal winding wound thereon;said toroidal winding a first and second concentric hollow conductivecylinder held ininsulated relationship with respect to one another. 3; Areactor comprisinga ring shaped core of mag-` neticmaterialand atoroidal winding wound thereon; said toroidal Winding having a first andsecond turn; each 'ofY said 'rst'and second turns including innerconductors and an outer conductor; connecting means for cyclicallyconnecting said inner conductors and outer conductor of said lirst andsecond turns tov form' said toroidal winding;V said inner conductors ofsaid first and second turns being radially displaced'from one another,the peripheral dimene sions of said first and second inner conductorsoverlapping one anotherV whereby the radialdimension of said first andsecond inner conductors may be substantially decreased for a requiredcross-sectional area to thereby decrease eddy current effects; saidfirst and second'inner conductors being formed of arespective hollowconductivegcylinder concentrically positioned with respect to one neticmaterial and toroidal winding wound thereon; said toroidal windinghaving a first and second turn; each of said first and second turnsincluding inner conductors and an outer conductor; connecting means forcyclically connecting said inner conductors of said lirst and secondturns and outer conductor of said irst and second turns to vform saidtoroidal Winding; said rst and second inner conductors being concentrichollow cylinders of relatively small radial dimension.

5.7A ommutating reactor comprising a ring shaped core of highlysaturableV type magnetic material and a toroidal winding wound thereon;said toroidal winding comprising a plurality of conductors of `smallradial dimension positioned within the opening formed by said ringshaped core, a plurality of outer conductors, and connecting conductors;said connecting conductors being constructed to interconnect `saidplurality of inner and outer conductors cyclically to torni a continuousconductor of toroidal form; said plurality of inner conductors beingconstructed'to form concentric. hollow cylinders.

References Cited in the ijle of tnl'spatent UNiTED STATES PATENTS11,320,980` Bowman 1 7.--- Nov. 4, 1917 17,994,767 Heintz Mar. 19, 19352,437,513 Gethmann M Oct. 12, 1946 2,709,791 Anderson May 31, 19552,759,128 Jensen 1 Aug. 14, 195

